Research On The Mechanism Of Physical And Chemical Permeability And Production Increase In Coalbed Methane Reservoir

China is rich in coalbed methane resources,but the development faces the problems of poor reservoir physical properties and easy blockage of production layers.The development effect of coalbed methane is poor.It is necessary to study the technical means of reservoir condition improvement and reservoir plugging removal.Taking the lump coal samples from Baode,Muai and Xinjiang as the research object,this paper summarizes the physical characteristics of lump coal samples in each area,optimizes the acidification and oxidation scheme suitable for each block reservoir through experimental means,and explores the CBM production effect after the reservoir improvement in Muai block combined with numerical simulation research.The results show that Muai block is high rank coal,Baode is low rank coal and Xinjiang is low rank coal.The plugging materials in Baode and Xinjiang blocks are mainly composed of ferrites,quartz and carbonate rocks,and Muai block is mainly composed of clay minerals.The acidification oxidation experiment of pulverized coal shows that the acidification effect of high-order coal is better than that of low-order coal,and the dissolution effect of acid on pulverized coal is hydrofluoric acid,hydrochloric acid and acetic acid from strong to weak.The recommended single acid parameters at the corresponding reservoir temperature are proposed for each block,and the corresponding acidizing and oxidation system is optimized for different blocks:the formula of Baode block is 10%HCl+2%CH₃COOH+2%HF+3%H₂O₂;The formula of Muai block is8%HCl+2%CH₃COOH+4%HF+3%H₂O₂;The formula of Xinjiang block is 12%HCl+1%CH₃COOH+1%HF+3%H₂O₂.Acidification and oxidation affect the porosity,permeability and wettability of coal samples.After acidification and oxidation,the porosity and permeability of lump coal samples in each area increase to a certain extent,and the porosity and permeability improvement effect of low rank coal is better than that of high rank coal.Acidification and oxidation have different effects on the wettability of coal.Acidification increases the hydrophilicity of coal,while oxidation will greatly reduce the hydrophilicity of coal.The hydrophilicity of coal samples treated by the preferred acidification and oxidation system is weakened.The numerical model of coalbed methane reservoir in Muai block is established.The reservoir parameters of the model are modified according to the acidification and oxidation effect obtained from the experiment.The recovery rate is increased by19.19%within 4 years,and the recovery effect of the treated reservoir is obvious.This paper has theoretical significance for the optimization of CBM acidizing reservoir system and unblocking reservoir in three blocks.